Surface and interface preparation and characterisation have become commonplace. Ultra-high vacuum facilities and much of the associated equipment, that would have been the most important and almost exclusive tools of the surface science specialists half a century ago, are nowadays widely used in many scientific and technological disciplines. Surface science on the other hand has expanded into areas that were not too long ago considered as being too “dirty” to be associated with this discipline, such as heterogeneous catalysis, solid/liquid interfaces and friction, electrochemical plating, corrosion, batteries and fuel cells, soft condensed matter and biology. Increasingly in the limelight are in situ observations of surface modifications and growth as well as structure-property relationships. Surface and interface science (SIS) is also naturally an integral part of nano-science, since the surface/interface to volume ratio of atoms/molecules is increasing strongly with shrinking size of objects. At the ESRF surfaces and interfaces are studied at about 50% of all beamlines. However, the three ESRF insertion device beamlines ID01, ID03, and ID32, which comprise the SIS group, and the CRG bending magnet beamline BM32 represent the specialists in this area.

2005 had been an important year for SIS at the ESRF. Following an intensive discussion with the SIS user community, it was decided at the end of 2004 to rigorously refurbish the surface X-ray diffraction beamline ID03. In 2005 this decision had to translate into action, and the most urgent task was to replace the personnel, which had left, and devise a strategy for the refurbishment. Now the beamline is again fully staffed. Two very experienced scientists and a second postdoc, an expert in surface crystallography, have been hired. For reconstruction, ID03 had been completely dismantled, but is by now back in place again with increased space for equipment. Towards the end of spring, it is scheduled to cater again to users with much improved optics and refurbished experimental facilities.

Progress and development can also be reported from the other two SIS beamlines. At ID32, focusing with compound refractive lenses for surface diffraction and Fresnel lenses for photoelectron spectroscopy are now available. A high-resolution secondary monochromator is presently being installed and a new state of the art primary monochromator is due to arrive in March 2006. At ID01 plans are taking shape to gear the beamline up to further explore the nano world with smaller focal spot sizes and by exploiting coherent scattering.

With scientific news from ID01 and the nano-world we are also starting the 2005 SIS highlights. Malachias et al. retrieve detailed quantitative information about the internal structure and the atomic ordering in Ge islands on silicon. Whereas bulk SiGe alloy is disordered, they find surprisingly ordered SiGe domains in the interior of the small islands. The way to establish order in assemblies of nano-particles, to find tricks to force inorganic matter to self organize, is in fact a big issue in current research. Leroy et al. report in the next contribution about a new method to achieve this. Using the UHV growth and in situ X-ray scattering facilities at BM 32 they demonstrate that a two dimensional array of dislocations can be employed for forcing an assembly of tiny magnetic dots to assemble into an ordered superstructure.

Three highlights are devoted to structure-property relations. Popa et al. employed surface X-ray diffraction at ID03 to shed light on the astonishingly different magnetic behaviour of ultra-thin cobalt and nickel films on a platinum surface. By solving the structure of the films they reveal the importance of magneto-elastic effects. Thiess et al. utilised X-ray photoelectron spectroscopy (XPS) and X-ray standing waves (XSW) at ID32 to carry out an investigation that seems impossible at first sight. They determined the sites of origin in the unit cell for electrons in specific parts of the strontium titanate valence band. The third highlight in this category is by Lechner et al.. They used anomalous X-ray diffraction at ID01 to resolve the relationship between the strain and the magnetic phase diagram in thin layers of magnetic semiconductors, which are materials, which may become the workhorses of future spintronic devices.

Fig. 92: Image of Mn within the cubic unit cell of GaAs.
Rendering of X-ray standing wave data taken at ID32.

The last two of the SIS highlights are dedicated to surface chemistry. Interfacing organic and inorganic matter is increasingly attracting interest, being of paramount importance to fields such as medicine. Hauschild et al. employed XSW in combination with XPS at ID32 to resolve the minute structural changes introduced into an organic molecule when it is bound to a silver surface. The last contribution underlines, that surface scientists, in the past “addicted” to UHV, now tackle the structure and properties of “real” surfaces. Ackerman et al. report about the investigation of a platinum catalyst during carbon monoxide oxidation, which is an exciting example in this respect. At ID03 they observed the associated structural changes of the surface at high temperature and close to atmospheric pressure. By monitoring the gas composition in the reaction chamber, they could intimately link the structural changes to changes in catalytic activity.

J. Zegenhagen